20 December 2019
Perihelion Distance (q)
Aphelion Distance (Q)
Click for NASA orbit diagram
Hills Observatory: 1 January 2013 to 15 February 2020
J. J. Blanpain (Marseille, France) discovered this comet in Virgo on 28 November 1819. The
comet was then situated in the morning sky. He estimated the diameter as 6-7 arc minutes,
and said a "very small and confused nucleus" was present. No tail was observed. Blanpain
confirmed his find on 29 November.
Blanpain only followed the comet until 2 December, but an independent discovery was made
on 5 December, by J. L. Pons (Marlia, Italy). He described the comet as small and faint, with
no tail or condensation. He continued making observations and other astronomers began to
observe the comet around mid-December, with A. Bouvard (Paris, France) first detecting the
comet on the 14th and P. Caturegli (Bologna, Italy) making his first observation on the 22nd.
Bouvard described the comet as very faint in his 7-cm refractor. Bouvard again saw the comet
in strong moonlight on the 30th and noted it was very faint. Pons obtained his final observation
of the comet on the 31st, the night of full moon. He described it as very faint, but the sky
clouded before he could measure its position.
As 1820 began, Bouvard and F. Carlini (Milan, Italy) were continuing observations. Bouvard's
last came on the morning of 15 January, when he noted the comet was extraordinarily faint in
his 7-cm refractor. Carlini obtained the last observation of the comet on 25 January. Several
other astronomers searched for the comet during January, but failed to find it. Most notably,
Pons had a clear morning on the 15th, but noted the comet had entered a region containing
Early parabolic orbits were calculated by F. Carlini and J. F. Encke. Their resulting perihelion
dates were 17 and 21 November 1819, respectively. Encke published the first elliptical orbit in
the 1824 volume of the Berliner Astronomisches Jahrbuch. Using seven positions obtained
between 14 December and 15 January, he determined a perihelion date of 20 November and
a period of 4.81 years. Several other astronomers have calculated elliptical orbits over the
years, with the most recent being I. Lagarde (1907). He began with the orbit computed by
Encke in 1824 and revised it to better fit the seven observations obtained between 14
December and 15 January. The result was an elliptical orbit with a perihelion date of 20
November and a period of 5.10 years.
A minor planet was discovered on 22 November 2003, by astronomers at the Catalina Sky
Survey (Arizona, USA). Five images obtained with the 68-cm Schmidt telescope and a CCD
camera revealed a stellar object with a magnitude ranging from 17.7 to 18.1. The object
passed 2.3 million miles from Earth on 12 December. At the beginning of 2004, M. Micheli
integrated the orbit of this object backwards and suggested it might be identical to Blanpain's
lost comet, although he revealed discordances of up to 17° in the argument of perihelion.
During February 2005, P. Jenniskens independently made the same suggestion, but showing a
much better fit with discordances of only 0.2°. B. G. Marsden quickly confirmed Jenniskens'
calculations and said the fit was possible with a purely gravitational solution.
The minor planet was next recovered on 4 July 2013, by astronomers using Pan-STARRS 1
(Hawaii, USA). They noted a stellar appearance and gave the magnitude as 20.1-20.2. On 7
July, G. V. Williams took 275 positions from the 1819, 2003, and 2014 apparitions, included
full planetary perturbations, and asssumed nongravitational terms of A1=+0.10 and
A2=-0.0054. He successfully linked all three apparitions, thus confirming that this was
Blanpain's lost comet.